Calculate the osmotic pressure of an aqueous solution containing 1g each of sucrose and glucose per `dm^(3)` at 300K. If this pressure was measured and it were not known that the solute was a mixture, what molecular weight would be expected ?

Answer

`pi=0.208" atm"; M=236.8"g mol"^(-1)`

Explanation

Mol. wt. of sucrose, `C_(12)H_(22)O_(11)=342`
Mol. wt. of glucose, `C_(6)H_(12)O_(6)=180`
Conc. of glucose, `C_(1)=(1)/(342)`,
Conc. of glucose `=(1)/(180), T=300K`
Total concentration`=C_(1)+C_(2)`
`=(1)/(342)+(1)/(180)=0.00292+0.00556=0.00848`
`pi=CRT=0.00848 xx 0.0821 xx300 =0.208` atm
Also, `pi=(w)/(M)RT=(2RT)/(M)`
or `M=(2RT)/(pi) = (2xx0.0821xx300)/(0.208)=236.8"g mol"^(-1)`